The purpose of the example was to show how the Prediction API can recognise the language used just from a few words. So, the data given to the API is a few words in French, and it's prediction is that the language is French. I believe that they're already using this technology in Google Translator. You just type in a few words and it immediately recognises what language is being used. Then you only need to choose the language to which the text is to be translated.